The test pipe / straight pipe is designed to remove your existing catalytic converter to enhance exhaust air flow (a test pipe is also referred to as a Cat Delete for this reason). The test pipe / straight pipe bolts right on to your stock header and exhaust without any modification. The Invidia test pipe provides increased amount of air flow through exhaust pipes to prevent any exhaust bottleneck. The test pipe / straight pipe is constructed of 100% polished stainless steel with a welded O2 bung for the stock O2 sensor.